1. Field of the Invention
The present invention relates to a method for manufacturing a silicon-on-insulator (SOI) substrate and a method for manufacturing a semiconductor device.
2. Description of the Related Art
In recent years, integrated circuits have been developed which use a silicon-on-insulator (SOI) substrate in which a thin single crystal semiconductor film is present over an insulating surface, instead of a bulk silicon wafer. The use of an SOI substrate can reduce parasitic capacitance between a drain of a transistor and a substrate; thus, SOI substrates are attracting attention for their ability to improve performance of semiconductor integrated circuits.
One of known methods for manufacturing SOI substrates is a hydrogen ion implantation separation method (for example, see Reference 1: Japanese Published Patent Application No. 2000-124092). A summary of a method for manufacturing an SOI substrate by a hydrogen ion implantation separation method is as follows. First, hydrogen ions are implanted into a silicon wafer by an ion implantation method to form a microbubble layer at a predetermined depth from the surface. Next, the silicon wafer into which hydrogen ions have been implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, by heat treatment, the microbubble layer serves as a cleavage plane and a part of the silicon wafer into which hydrogen ions have been implanted is separated in a thin film shape along the microbubble layer. Accordingly, a single crystal silicon film can be formed over the other bonded silicon wafer.
A method for forming a single crystal silicon layer over a base substrate made from glass by using such a hydrogen ion implantation method as described above has been proposed (for example, see Reference 2: Japanese Published Patent Application No. 2004-87606). Glass substrates can be manufactured in larger sizes and are less expensive than silicon wafers. Thus, the use of a glass substrate as a base substrate makes it possible to manufacture a large-sized inexpensive SOI substrate.